GetSpellCooldown() for party members

[Lolzen]

I'm assuming on my tests GetSpellCooldown() is restricted to known spells, however nothing in the documention specifically states this as an fact.
Is it restricted that way?

If so, is there anything i can use to get a cooldown from a spellid which does NOT have these restrictions?

https://github.com/Lolzen/Namerakana...aster/core.lua
unfinished, unpolished, sligthly out of date, etc. just for reference